diff --git a/cheapest_ticket.py b/cheapest_ticket.py
index 320d1ed..b6279c0 100755
--- a/cheapest_ticket.py
+++ b/cheapest_ticket.py
@@ -5,32 +5,46 @@ import sys
 
 import captaintrain as ct
 
+def usage():
+    print("""cheapest_ticket.py departure-station arrival-station departure-date
+
+    departure-date: any string parsable by date -d
+""")
 
 if __name__ == "__main__":
-    if len(sys.argv) > 3:
-        departure = ct.station(sys.argv[1])
-        arrival = ct.station(sys.argv[2])
-        departure_time = 0
+    if len(sys.argv) <= 3:
+        usage()
+        sys.exit(1)
 
-        with subprocess.Popen(["date", "-d", sys.argv[3], "-u", "-Iseconds"], stdout=subprocess.PIPE) as f:
-            departure_time = f.stdout.read().strip().decode()
+    departure = ct.station(sys.argv[1])
+    if departure is None:
+        print("Unknown station '%s'" % sys.argv[1])
+        sys.exit(1)
 
-        if departure_time == 0 or departure_time == "":
-            sys.exit(1)
-        else:
-            departure_time = ct.parse_datetime(departure_time)
+    arrival = ct.station(sys.argv[2])
+    if arrival is None:
+        print("Unknown station '%s'" % sys.argv[2])
+        sys.exit(1)
 
-        print("From:", departure.name, departure.id)
-        print("To:", arrival.name, arrival.id)
-        print("Departure:", departure_time)
+    departure_time = 0
 
-        #with open("res.json") as f:
-        #    import json
-        #    res = ct.Search(**json.load(f))
+    with subprocess.Popen(["date", "-d", sys.argv[3], "-u", "-Iseconds"], stdout=subprocess.PIPE) as f:
+        departure_time = f.stdout.read().strip().decode()
 
-        res = ct.search(departure, arrival, departure_time)
-        min_trips = ct.cheapest_trips(res.trips)
-        for trip in min_trips:
-            print(trip)
+    if departure_time == 0 or departure_time == "":
+        sys.exit(1)
     else:
-        print("usage")
+        departure_time = ct.parse_datetime(departure_time)
+
+    print("From:", departure.name, departure.id)
+    print("To:", arrival.name, arrival.id)
+    print("Departure:", departure_time)
+
+    #with open("res.json") as f:
+    #    import json
+    #    res = ct.Search(**json.load(f))
+
+    res = ct.search(departure, arrival, departure_time)
+    min_trips = ct.cheapest_trips(res.trips)
+    for trip in min_trips:
+        print(trip)